Vasodilators: Scorpion envenoming and the heart
(An Indian Experience)
(Received for publication 11 March 1994)
Our aim was to assess clinically whether there was any benefit in adding a single dose of sublingual nifedipine (a slow calcium channel blocker) to prazosin in the management of the cardiovascular manifestations of envenoming by the Indian red scorpion (Mesobuthus tamulus). A total of 163 patients stung by this species was admitted to the hospital at Mahad between January 1991 and October 1993.

Cardiovascular abnormalities were hypertension (59), of whom 42 had brady cardia and 17 had tachycardia, pulmonary oedema (14), of whom eight had hypertension and six hypotension, supraventricular tachycardia (eight), of whom three had hypotension and one died. Of the remaining patients, 78 demonstrated severe excruciating local pain at the site of sting but had no systemic involvement. Nineteen patients with hypertension and tachycardia were given a single dose of sublingual nifedipine plus prazosin on admission, then prazosin alone repeated 6 hourly. Five patients with massive life threatening pulmonary edema recovered after being given intravenous sodium nitroprusside. Prazosin alone helped to alleviate cardiovascular manifestations in the remaining 42 victims.

One patient was admitted in a deep coma, 12 hr after the sting, and died. Eight victims whose blood pressure had been controlled in hospital by nifedipine plus prazoin for recovery. Fifty two victims treated with prazosin alone did not develop pulmonary edema and the drug appeared to hasten the recovery. In the presence of high blood pressure, tachycardia, a murmur and impending myocardial failure, nifedipine appeared to contribute to cardiopulmonary instability and to augment myocardial oxygen consumption. In this situation calcium channel blockers should probably be avoided.

Introduction
Scorpion envenoming is common in many parts of the world (Amitai et al., 1984, Poonking, 1963, Gueron et al., 1967, Mundle, 1961). Primary health where medical aid is first sought by villagers deal with the largest number of cases (Gaitonde et al.,1978, Bawaskar and Bawaskar, 1989). Envenoming by Mesobuthus tamulus has a fatality rate of 30 to 54% (Mundle, 1961, Bawaskar, 1977, Rajarajeswari et al., 1979, Karnad et al., 1989). These accidents usually occur during the night because scorpions are nocturnal. For medical help, villagers have to travel 10 to 20 miles or more. As cardiovascular morbidity and mortality depends upon the time lapse between sting and hospitalization (Bawaskar and Bawaskar, 1991), we believe that the delay in transport of these patients to the nearest large hospital contributed to their death (Bawaskar, 1982). We would stress the importance of the cardiotoxic effects of scorpion sting and their pharmacological management within the limited resources available in health centers.

We have been treating victims of scorpion envenoming since 1976. Between 1976 and 1983 we used digoxin, diuretics, steroids, atropine, antihistamines, propranlol, chlorpromazine and medical phlebotomy. Eleven out of 81 patients with cardiac problems died. Between 1984 and 1990, 18 out of 323 patients with cardiac problems died. The addition of prazosin and isosorbide dinitrate possibly improved the prognosis. In the present study, carried out between 1991 and October 1993, one out of 163 died of cardiac problems. Early administration of prazosin and avoidance of routine use of atropine, digoxin, steroids and antihistamines has improved the prognosis. Reduction in morbidity and mortality in Maharashtra region has been achieved by providing recent relevant publications, and arranging periodic discussions, slide demonstrations and lectures to doctors practicing in villages, to medical associations and to medical colleges (Bawaskar and Bawaskar, 1992 b). In our series, not a single victim died to cardiac arrhythmias or arrest once the pharmacological effects of prazosin occurred. Thus, we do not advocate routine admission and treatment of these victims in an intensive are unit. Such facilities are beyond the reach of villagers.

Subjects
One hundred and sixty three patients accidentally stung by Indian red scorpions (Mesobuthus tamulus) were admitted to hospital at Mahad. Soon after being stung, 85 patients developed vomiting, profuse sweating (sweat literally flowing from the body), and priapism in males, all suggestive of cholinergic activity and mild local pain with edema at the site of the sting. The other 78 had severe excruciating pain at the site of the sting, which radiated to the corresponding dermatomes, but no signs and symptoms suggestive of systemic involvement. None of these victims had abnormal electrocardiograms. Local pain was treated by injecting 0.1–0.2 ml of dehydroemetine hydrochloride at the site of sting because this treatment gives more prolonged relief from pain tan des a local anesthetic agent. The 85 victims with systemic involvement were admitted, and the following were closely monitored clinically: heart rate, blood pressure, persistent parasternal systolic lift, systolic murmur, gallops, rales in chest, priapism, the appearance of skin and mucous membranes and the temperature of the extremities. According to major clinical manifestations, patients were divided into five groups.

Hypertension with bradycardia
Forty two patients (28 m, 14F), aged 6–85 (average 30) years, reported 1.5–8 (average 2.5) hr after the sting with blood pressures between 140/100 and 210/160 mmHg. Their heart rates were 58–83 (average 67) beats per min. They seemed frightened, had prominent eyes and puffy faces, and complained of parasthesiae around their mouths and extremities and at times all over the body. The children were confused and agitated, looked lethargic and had oculogyric phenomena.